Nanoparticles have unique physical properties unlike properties of bulk and atomic species, and various studies of nanomaterials have been increasingly conducted around the world. An application of nanomaterials to various fields such as electrochemistry, microelectronics, optics, bionics, etc. has been on the rise since nanomaterials have unique physical properties. Particularly in electronic applications, various substrates are applied to manufacture electronics parts recently. Accordingly, a nanomaterial is needed for forming fine wiring on a thin film by various printing methods. In general, lithography is used for printing a pattern on a substrate but the complicated process increases the process price. Therefore, an electrically conductive metal ink capable of being printed as a pattern on a film directly without a complicated process is urgently needed.
Furthermore, in addition to formation of fine wiring, inclusion of a heat integration phenomenon has been intensified in the electronic industry due to miniaturization and high power output of electric/electronic components and integration of electronic components, such that interest has increased in high heat dissipation materials for preventing malfunction of electronic component due to heat integration. In particular, the heat dissipation body is composed of semiconductor components such as power transistor, thermistor, printed wiring board, and integrated circuit (IC), etc. and also electric/electronic components such as heat dissipation material containing epoxy resin and inorganic filler. Such heat dissipation materials are required to have superior strength and thermal conductivity.
Thermal conductive and electrical conductive ink materials mainly used in the industry are noble metals such as silver (Ag), gold (Au), platinum (Pt), etc. which have high thermal conductivity, electrical conductivity, and low degree of oxidation, whereby it is known that noble metals are capable of being applied to printing process directly. However, noble metals have limit in manufacture of ultra-fine wiring circuit due to high price and ion migration phenomenon. Non-noble metals such as copper (Cu), nickel (Ni), aluminum (Al), etc. having similar thermal conductivity and electrical conductivity of noble metals are used to solve such problems since non-noble metals enable designing a ultra-fine wiring and are cheaper than noble metals. Despite of such merits of non-noble metals, manufacturing cost is increased due to high degree of oxidation thereof, so commercialization of noble metals is difficult.
A step of sintering a substrate, in addition to prevention of surface oxidation, is also one of processes to be solved in a method of manufacturing a conductive film. A conductive ink containing metal particles is subjected to a sintering process in which conductivity is imparted through a connection between metal particles by using heat or light energy after being printed on an insulating substrate. Noble metal based-conductive ink having a low degree of oxidation can be sintered under atmosphere generally, while non-noble metal-based ink having high degree of oxidation is needed to be sintered under an inert gas atmosphere, a hydrogen gas atmosphere, or vacuum. A related art is known in Korea Patent No. 10-1418276, entitled “Synthetic method of preventing metal nano-particle from having oxidized film and method of forming conductive metal thin film via solution-processed”. The related art provides forming a conductive film by sintering under an argon and hydrogen atmosphere using a copper-based conductive ink provided with a surface oxidation prevention film thereon. However, when sintering is performed in such inert gas atmosphere, the manufacturing cost is increased compared with the process under the general atmosphere.
In addition, a related art known as Korea Patent No. 10-0775077, entitled “Positive polar materials and its manufacturing method of Li-secondary battery” provides that a stabilized oxide layer is additionally formed for prevention of oxidation. However, when the oxide layer is formed as described above, an additional process and material are needed so a manufacturing process becomes complicated and manufacturing cost is increased.